Pathomorphologial investigation of spondylolisthesis leaded to spondylosis in commercial broiler chicken with posterior paralysis: A case study.

Spondylolisthesis known as kinky back syndrome is a deformity of the free sixth thoracic vertebra including enlargement and rotation resulting in posterior paralysis in broiler chicken. Genotype, feeding regimes and environment are involved in occurrence of this congenital anomaly. Spondylolisthesis may result in or happen simultaneously with two other major axial skeleton pathologies including spondylosis and spondylitis as a result of occurrence of degenerative necrobiotic lesions and inflammation of the vertebrae, respectively. This report deals with a male broiler chicken with posterior paralysis in the second week of rearing. After euthanasia, the specimen was evaluated at macroscopic and microscopic levels. Macroscopic findings showed the unilateral enlargement of body and transverse process of sixth thoracic vertebra and downward rotation of the body. The histopathological studies revealed the focal chondronecrosis and degenerative changes in articular facets and cranial process of the vertebra. In conclusion, a diagnosis of spondylolisthesis followed by spondylosis was made based on macroscopic and histopathological findings that to the authors' best knowledge, is the first report in a broiler farm in Iran.